1. Field of the Invention
The present invention generally relates to an object detection system for a vehicle.
2. Description of Related Art
Automotive remote sensing systems are being developed to provide a variety of functional features involving the detection of objects in the near vicinity of the host vehicle. These remote sensing systems can be referred to as near obstacle detection systems (NODS). Individual NODS applications can provide various functional features such as side object detection, parking assistance, backup assistance, and pre-impact sensing. For these NODS applications, the sensing system is responsible for detecting and locating objects within a defined detection zone around the vehicle. The size and shape of the detection zone for which the sensing system must provide coverage varies with the functional features provided by the NODS application. For example, FIG. 1 shows the potential detection zones for various NODS applications. These zones include side object detection 12, side pre-impact 14, front park aid 16, stop and go cruise control 18, and backup/rear parking aid 20 located at various positions relative to the vehicle 10.
Many of the detection zones, in FIG. 1, are at least partially square or trapezoidal in shape. This poses a compatibility issue for many sensor technologies. Typically, a mismatch exists between the sensors coverage area, which is commonly defined by the sensor's radiation pattern or optical field of view, and the desired detection zone. Simple sensing systems which utilize radar, ultrasonic, capacitive, and certain types of infrared technologies provide coverage areas which are more elliptical or lobed in shape.
The side object detection zone 12 will be used to further illustrate the problem. FIG. 2 illustrates the detection zone for a typical side obstacle warning application. The dimensions of the side object detection zone 12 are dependent upon the desired level of system functionality, as well as, the dimensions of the particular host vehicle 10. For example, a side obstacle warning system designed to notify drivers of adjacent obstacle maneuvers would typically have a length extending from the location of the outside rearview mirror to several meters behind the rear bumper of the vehicle. The width would extend from the vehicle surface to perhaps ¾ of the adjacent lane. In the sample dimensions of FIG. 2, the detection zone extends from the outside rearview mirror, six meters towards the rear of the vehicle, and 3.5 meters towards the adjacent lane.
FIG. 3 illustrates the mismatch problem between a simple sensor coverage area, in the case of a radar radiation pattern, and the desired side obstacle warning detection zone. In FIG. 3, the coverage area 21 is depicted in the form of a lobed shape as would be provided by a simple, single beam radar sensor. An object located within the coverage area 21 will be detected by the radar and its range can be obtained by a number of widely known methods. The arc 23 in the coverage area 21 is a constant range from the sensor and defines a sensing zone 22. The range information is used to determine whether an object is located within arc 23 defining sensing zone 22. As such, the sensing zone 22 is used to approximate the desired side object detection zone 12. For example, when an object is detected within a specified range, it is declared to be within the side object detection zone 12, otherwise it is declared not to be in the side object detection zone 12. The problem with this type of implementation is clearly evident, the mismatch between the sensor's sensing zone 21 and the desired side object detection zone 12 results in substantial missed detection areas 26 or false alarm areas 24.
In view of the above, it is apparent that there exists a need for an improved object detection system.